The Stressor Identification Process

2 Define the Case List Candidate Causes Evaluate Data from the Case Evaluate Data from Elsewhere Identify Probable Cause Detect or Suspect Biological Impairment As Necessary: Acquire Data and Iterate Process Identify and Apportion Sources Management Action: Eliminate or Control Sources, Monitor Results Biological Condition Restored or Protected Decision-maker and Stakeholder Involvement Stressor Identification The causal analysis framework

3 Define the Case List Candidate Causes Evaluate Data from the Case Evaluate Data from Elsewhere Identify Probable Cause As Necessary: Acquire Data and Iterate Process Identify and Apportion Sources Management Action: Eliminate or Control Sources, Monitor Results Biological Condition Restored or Protected Decision-maker and Stakeholder Involvement Stressor Identification Detect or suspect biological impairment Fish kills Organismal anomalies Changes in community structure Low biotic index values Violation of biocriteria

4 ‘98 303(d) List Public-Owned Treatment Works (POTW) main focus TMDLs target Cu, Pb, Zn POTW Willimantic River case study

5 POTW Willimantic River case study MR 3 MR 1 Impaired site MR3 (↓ EPT taxa) Less impaired site (MR1) upstream of MR3

6 6 Triggering the causal analysis moderately impaired

7 Step 1: Define the Case List Candidate Causes Evaluate Data from the Case Evaluate Data from Elsewhere Identify Probable Cause Detect or Suspect Biological Impairment As Necessary: Acquire Data and Iterate Process Identify and Apportion Sources Management Action: Eliminate or Control Sources, Monitor Results Biological Condition Restored or Protected Decision-maker and Stakeholder Involvement Stressor Identification What biological effects are observed? Where are they occurring? Where are comparable reference sites?

8 8 Example: defining the biological impairment in the Willimantic case study Biological effect MR1 (reference) MR3 (impaired) Change Number of EPT taxa 179decrease

Making the impairment specific The more specific you can make—or the more narrowly you can define—the impairment, the better. Specific = better discrimination across candidate causes Can consider multiple impairments Level of specificity ExamplesUtility in SI LOWFailure to meet biocriteriaTriggers SI ↓ sensitive taxa ↓ EPT richness Listing candidate causes Developing conceptual model HIGH ↓ Paraleptophlebia Absence of brook trout Grouping sites Diagnosing causes Evaluating strength of evidence

10 Define the Case Evaluate Data from the Case Evaluate Data from Elsewhere Identify Probable Cause Detect or Suspect Biological Impairment As Necessary: Acquire Data and Iterate Process Identify and Apportion Sources Management Action: Eliminate or Control Sources, Monitor Results Biological Condition Restored or Protected Decision-maker and Stakeholder Involvement Stressor Identification Step 2: List Candidate Causes Make a map Gather information on potential sources, stressors, & exposures Develop a conceptual model Engage stakeholders

11 Focus on stressor(s) that may be causing biological impairment May have causal scenarios, with several stressors acting in combination Candidate causes may include: – Mechanisms or modes of action – Sources Listing candidate causes

12 MR3 MR1 POTW Stafford Springs woods industrial facility farms Example: the Willimantic River case study

13 ↑ other toxics Example: using models for communication ↓ dissolved oxygen ↑ temperature ↓ EPT richness POTW industrial facility damssubdivisiondairy farm ↑ NH 3 ↑ Zn

14 ↑ other toxics Example: using models for communication ↓ dissolved oxygen ↑ temperature ↓ EPT richness POTW industrial facility damssubdivisiondairy farm ↑ NH 3 ↑ Metals Evidence?

15 Define the Case List Candidate Causes Evaluate Data from Elsewhere Identify Probable Cause Detect or Suspect Biological Impairment As Necessary: Acquire Data and Iterate Process Identify and Apportion Sources Management Action: Eliminate or Control Sources, Monitor Results Biological Condition Restored or Protected Decision-maker and Stakeholder Involvement Stressor Identification Step 3: Evaluate Data from the Case EVIDENCE FROM THE CASE Co-occurrence Exposure or mechanism Causal pathway Stressor-response relationships from field Manipulation Lab tests of site media Temporal sequence Verified predictions Symptoms

Supports Weakens Spatial/Temporal Co-Occurrence Upstream Downstream Comparison Physical Interaction Causal agents change an affected agent by physical interaction.

17 Spatial/Temporal Co-Occurrence Adverse change compared to references 1. Toxics Upstream reference Watershed reference Impaired site UpstreamWatershed Al Yes a 8/28/00 b 7/23/01

18 Spatial/Temporal Co-Occurrence Candidate Cause Measurement Upstream reference Watershed reference Impaired site Adverse change compared to references 1. Toxics Total Metals and Ammonia (mg/L) MR1RB1MR3MR1RB1 Al Yes Cd000No Cr Yes Cu Yes Fe Yes Ni No Pb NoYes Zn Yes NH No a 8/28/00 b 7/23/01

19 Spatial/Temporal Co-Occurrence Spatial co-occurrence Candidate Cause Measurement Upstream reference Watershed reference Impaired site Advance change compared to references 2: High Flow No Evidence MR1 RB1MR3MR1RB1 3: Embeddedness % Silt Covered Substrate 0-25% 50-75%Yes 4: Low Dissolved Oxygen Minimum Dissolved Oxygen (mg/L) 7.32 b b 8.91 b NoYes 5: Temperature Stress Maximum Temperature o C b o C a o C b Yes 6: Altered food resource No Measurements a 8/28/00 b 7/23/01

20 Loss of suitable habitat Increased amount of fine particles Fine particles fill interstitial spaces Impoundment Increased algae Road Sanding Loss of invertebrates Bank Failure Decreased inter- gravel dissolved oxygen Particle settling Impoundment filling and particle export More EPT taxa at MR2 downstream from dam and upstream from MR3 Proportion of substrate composed of sand was half the amount observed at the upstream reference site Bank stability score was unchanged from upstream; stream banks armored by riprap and granite walls XXX Sequential Dependence All effects result of a prior sequence of cause effect events loss of interstitial habitat due to settled particles

21 Define the Case List Candidate Causes Evaluate Data from the Case Identify Probable Cause Detect or Suspect Biological Impairment As Necessary: Acquire Data and Iterate Process Identify and Apportion Sources Management Action: Eliminate or Control Sources, Monitor Results Biological Condition Restored or Protected Decision-maker and Stakeholder Involvement Stressor Identification Step 4: Evaluate Data from Elsewhere EVIDENCE FROM ELSEWHERE Stressor-response relationships (from lab, other field studies, or ecosystem models) Mechanistically plausible cause Manipulation at other sites Analogous stressors

Stressor-Response Relationships from Laboratory Studies Weakens Strengthens Sufficiency The intensity or frequency of a cause is adequate to produce the observed magnitude of effect. Supports

23 Stressor-Response Relationships from Laboratory Studies CT Values (ug/L) Daphnids (ug/L) Test EC20MR1 Exceeded at MR1 MR3 Exceeded at MR3 AlNone No107No Cd Yes0.5 Yes Cr100< No2 Yes Cu Yes2.5 Yes FeNone No532No Ni88<5450.2No0.3No Pb No0.8No Zn No8.6No NH No100No

24 Impairment is so great, exposure to some agent at highly adverse levels must be occurring. Natural variability could not account for this. EffectImpaired site Number of EPT Taxa 9 Lacking Sufficiency from Analogous Situations

25 Prediction from Analogous Situations Experience suggests that highly toxic exposures are involved. 1. Bracket site, look for origination of impairment. 2. At the origination, there should be a point source, not non- point source. 3. The point source will intermittently release a highly toxic pollutant or precursor. EffectImpaired site Number of EPT Taxa 9

26 Verified Predictions of Source Illicit discharge observed upstream from impairment Sequential Dependence All effects result of a prior sequence of cause effect events

27 Manipulation of Source/Exposure SUPPORTS Impairment occurs when stressor present and does not occur when stressor is removed WEAKENS Impairment occurs when stressor present and when stressor is removed

MR2MR3WL Mean number of EPT taxa before ( ) & after ( ) rerouting of illicit discharge Sequential Dependence All effects result of a prior sequence of cause effect events Manipulation of Source/Exposure

29 Define the Case List Candidate Causes Evaluate Data from the Case Detect or Suspect Biological Impairment As Necessary: Acquire Data and Iterate Process Identify and Apportion Sources Management Action: Eliminate or Control Sources, Monitor Results Biological Condition Restored or Protected Decision-maker and Stakeholder Involvement Stressor Identification Step 5: Identify Probable Cause Evaluate Data from Elsewhere Weigh strength of evidence for each cause –eliminate if you can –diagnose if you can Compare strength of evidence across causes

30 Willimantic case study MetalsNH 3 FlowSiltLow DO TempFoodEpisodic Mix Types of Evidence that Use Data from the Case Spatial/Temporal Co-Occurrence Evidence of Biological Mechanism Causal Pathway Stressor-Response from the Field Manipulation Verified Predictions Types of Evidence that Use Data from Elsewhere Stressor-Response from Other Field - + Stressor-Response from Laboratory Example: strength of evidence analysis

31 How to evaluate consistency of evidence Candidate cause Type of evidenceNH 3 CuTSS Co-occurrence +–+ Causal pathway +–– Manipulation +–+ Stressor-response +–– CONSISTENCYsupportsweakens

Willimantic case study MetalsNH 3 FlowSilt Low DO TempFood Episodic Mix Types of Evidence that Use Data from the Case Spatial/Temporal Co-Occurrence Evidence of Biological Mechanism Causal Pathway Stressor-Response from the Field Manipulation of Co-occurrence Verified Predictions Types of Evidence that Use Data from Elsewhere Stressor-Response from Other Field - + Stressor-Response from Laboratory Evaluating Multiple Types of Evidence Consistency of Evidence

33 ↑ other toxics Example: using models for communication ↓ dissolved oxygen ↑ temperature ↓ EPT richness POTWdamssubdivisiondairy farm ↑ NH 3 ↑ Cd DO higher at impaired site vs. reference industrial facility after rerouting industrial discharge had decreased concentrations of Zn & other toxics, increased EPT taxa richness NH 3 same at impaired site and references. Cd greater at impaired site vs. reference, but not at levels sufficient to cause impairment

34 Define the Case List Candidate Causes Evaluate Data from the Case Evaluate Data from Elsewhere Identify Probable Cause Detect or Suspect Biological Impairment As Necessary: Acquire Data and Iterate Process Identify and Apportion Sources Management Action: Eliminate or Control Sources, Monitor Results Biological Condition Restored or Protected Decision-maker and Stakeholder Involvement Stressor Identification Causal analysis is one step in management process… After causes are identified, sources & management actions must be identified Biological monitoring verifies that actions are effective

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